Drilling tools are used to drill cylindrical holes in metallic workpieces. The cutting or boring action of the drill tools may be carried out by an elongated, substantially cylindrical drilling tool, such as a combination of a tool holder and a drill insert, which is selectively attached thereto. Such an arrangement may then be used in an application wherein one end of the tool holder is securely mounted in a driving apparatus, which rotates the holder about its longitudinal axis. At the opposite end of the elongated tool holder, the cutting insert engages the material to be cut. Alternatively, the workpiece may be made to rotate relative to the holder and cutting insert, such as in positioning the holder in the tail stock of a lathe or the like. Further, the tool and workpiece may be made to rotate relative to one another. The use of cutting inserts allows for quick changing of the insert upon wear of the cutting surfaces instead of the entire tool, and allows for one tool to be used for a variety of different boring applications by simply changing the insert and not the entire drill assembly.
The indexable drill inserts plays a very important role in drilling because all the sides of insert can be used for cutting one after the other. Further, use of inserts will reduce the manufacturing lead time and assembling time.
The use of quadra angular indexable drill inserts are known in the art. However, the inserts which are in the art comprises four rectangular cutting edges for cutting the workpiece. The use of rectangular cutting edges makes the drill to drift away from its centre because the forces are acting all over the drill body and not exactly at the centre. The drill drift further creates a narrow wall which is not feasible in practical applications. Further, the conventional indexable drill inserts rub the surface of the drilling hole if the diameter of the drill hole is less than the predetermined value.
Further, when the conventional quadra angular indexable drill inserts are mounted such that portion of the drill insert crosses centre of the drill body it forms reverse cutting operation. During drilling operation corners of the drill insert would chip out due to reverse cutting action.
In the view of above mentioned disadvantages it is necessary to develop a drill insert having four identical cutting edges